A method for in-situ measurement of surface topography of a hemispherical resonator based on a tympanum grating interferometer

Abstract

The application discloses a kind of in-situ measurement methods of hemispherical resonator surface topography based on thurn gullin interferometer, it is related to ultra-precision grinding and polishing processing technical field, to solve the problem of lacking non-contact hemispherical resonator surface topography in-situ measurement method in prior art.The in-situ measurement method of the present application is based on the in-situ measurement system of integrated thurn gullin interferometer and hemispherical resonator ultra-precision grinding and polishing machine tool, for the hemispherical resonator after polishing, by controlling machine tool to make thurn gullin interferometer measure the sub-aperture surface shape of all annular regions of hemispherical resonator, then splice all sub-aperture surface shape data, obtain the annular region topography of hemispherical resonator, realize the non-contact in-situ measurement of hemispherical resonator surface topography.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision grinding and polishing technology, and more specifically, to an in-situ measurement method for the surface morphology of a hemispherical harmonic oscillator based on a Thyman-Green interferometer. Background Technology

[0002] The hemispherical resonator gyroscope is currently the most precise solid-state resonator gyroscope, possessing outstanding advantages such as high reliability, long lifespan, strong shock resistance, and intrinsic radiation resistance. It meets the long-endurance development requirements of next-generation inertial devices. It mainly consists of a hemispherical resonator, force electrodes, and pickup electrodes (detectors). The hemispherical resonator is the core component of the hemispherical resonator gyroscope. It is a thin-walled hemispherical shell with a central anchor, with a diameter ranging from 15-60 mm and a wall thickness typically from 0.3-1.1 mm. Under the electromagnetic force of the force electrodes, the hemispherical resonator deforms and generates an elastic standing wave. When a moving object drives the hemispherical resonator gyroscope to rotate, the rotation angle of the standing wave mode will be proportionally smaller than the rotation angle of the moving object, depending on the angular velocity. The pickup electrodes can measure the change in the mode angle, and the computer can calculate the rotation angle of the moving object.

[0003] High-quality fused silica is the best material for manufacturing hemispherical resonators, as it has low internal friction, high hardness, and excellent density and elastic isotropy. The manufacturing process of a hemispherical resonator mainly includes rough grinding and fine grinding, polishing and chemical etching, quality leveling, surface coating, and Q-value testing. The dimensional accuracy after grinding can only reach the micrometer level, and it also creates a deep damage layer on the surface, failing to meet the requirement of uniform mass distribution along the rotation axis of the hemispherical resonator. Therefore, magnetorheological polishing is needed to remove the stress and damage layer caused by machining, reduce surface roughness, and simultaneously ensure the shape accuracy of the polished parts, giving the inner surface of the resonator shell high surface accuracy.

[0004] Currently, research on the fabrication of hemispherical resonators is still in the exploratory stage, and there is limited research on the measurement of the surface morphology of hemispherical resonators. Existing patent CN 115540735 A discloses an in-situ measurement method for the concentricity and thickness uniformity of the inner and outer spherical surfaces of a hemispherical resonator, using an inductive lever probe. However, the inductive lever probe is a contact measurement method, which is prone to damaging the fabricated surface of the hemispherical resonator. Existing patent CN 112729159A discloses a method for detecting the spherical surface shape of a hemispherical resonator, achieving high-precision measurement of the entire spherical annulus on the inner and outer surfaces of the hemispherical resonator using a laser interferometer and a parabolic standard mirror. However, it cannot achieve in-situ surface shape detection of the hemispherical resonator. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] There is a lack of non-contact in-situ measurement methods for the surface morphology of hemispherical harmonic oscillators in the existing technology.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] This invention provides an in-situ measurement method for the surface topography of a hemispherical harmonic oscillator based on a Thurman-Green interferometer. The in-situ measurement method is based on an in-situ measurement system integrating a Thurman-Green interferometer and an ultra-precision grinding and polishing machine tool for hemispherical harmonic oscillators, and includes the following steps:

[0009] S100. For the polished hemispherical resonator, adjust the X-axis linear motion platform, Y-axis linear motion platform, Z-axis linear motion platform, C-axis turntable and U-axis micro-displacement platform so that the center of the hemispherical resonator coincides with the focal point of the lens of the Thyman Green interferometer.

[0010] S200: The C-axis turntable drives the Thyman Green interferometer to rotate, so that the field of view of the Thyman Green interferometer includes part of the circumferential region of the hemispherical harmonic oscillator.

[0011] S300. Determine the initial measurement position of the hemispherical harmonic oscillator and measure the sub-aperture surface shape at the initial position using a Thyman Green interferometer.

[0012] S400: The workpiece spindle drives the hemispherical resonator to rotate. The Thyman Green interferometer is used to measure the surface shape of the current sub-aperture. There is an overlap between two adjacent sub-apertures.

[0013] S500. Repeat step S4 until the entire circumferential region of the hemispherical harmonic oscillator is measured.

[0014] S600: By splicing together all the sub-aperture surface data, the circumferential region morphology of the hemispherical harmonic oscillator is obtained.

[0015] Further, step S100 includes the following steps:

[0016] S110. For the polished hemispherical resonator, the relative position of the C-axis turntable and the hemispherical resonator is determined by the tool setting operation, and the X-axis linear motion platform and Y-axis linear motion platform are adjusted so that the center of the hemispherical resonator coincides with the rotation axis of the C-axis turntable.

[0017] S120. Adjust the Z-axis linear motion platform so that the focal point of the Thyman Green interferometer lens is at the same horizontal level as the center of the hemispherical harmonic oscillator.

[0018] S130. Adjust the U-axis micro-displacement platform so that the focal point of the Thyman Green interferometer lens coincides with the center of the hemispherical harmonic oscillator.

[0019] Furthermore, in S400, the overlap between two adjacent sub-apertures accounts for 20% of the sub-aperture area.

[0020] Furthermore, the sub-aperture stitching algorithm includes the following steps:

[0021] The measurement data for the sub-apertures of the interferometer are (x, y, z), where (x, y) are the horizontal and vertical coordinates on the image plane, and z is the height value; the measurement data for the k-th sub-aperture is (x...y...z). k ,y k ,z k The measurement data for the t-th sub-aperture is (x t y t , z t );

[0022]

[0023] Where g is the pose transformation matrix; (x q y q , z q () represents the coordinates of the sub-aperture data of the hemispherical harmonic oscillator in the global coordinate system;

[0024] In the global coordinate system, the measurement data deviation in the sub-aperture overlap region is:

[0025] d=<(x k ,y k ,z k )-q,n>-<(x t y t , z t )-q,n>

[0026] Where {q} is the point set projected from the medium aperture measurement data onto the surface of the hemispherical harmonic oscillator, and n is the unit normal vector of the hemispherical harmonic oscillator surface at position q; <(x k ,y k ,z k )-q,n> is a vector (x k ,y k ,z k The inner product of q and vector n; <(x) t y t , z t )-q,n> is a vector (x k ,y k ,z k The dot product of -q and vector n;

[0027] Based on the least squares method, the measurement data deviation in the overlapping region of the sub-apertures is minimized to obtain the surface morphology of the hemispherical harmonic oscillator;

[0028]

[0029] Where, N oThis represents the total number of overlapping point pairs.

[0030] Furthermore, the in-situ measurement system integrates a hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool and a Thyman Green interferometer. The hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool includes a machine bed, an X-axis linear motion platform, a Y-axis linear motion platform, a Z-axis linear motion platform, a C-axis rotary table, a U-axis micro-displacement platform, a workpiece spindle, a tool spindle, a triangular connecting frame, a fixed frame, and a worktable.

[0031] The machine tool bed is equipped with an X-axis linear motion platform, a Y-axis linear motion platform and a Z-axis linear motion platform. The X-axis linear motion platform and the Y-axis linear motion platform are stacked in a cross shape. The Z-axis linear motion platform is installed perpendicular to the X-axis linear motion platform and the Y-axis linear motion platform, together forming a spatial rectangular coordinate system.

[0032] The worktable is mounted on the X-axis linear motion platform and the Y-axis linear motion platform;

[0033] The workpiece spindle is mounted on the worktable, and the rotation axis of the workpiece spindle is parallel to the Y-axis.

[0034] The C-axis turntable is mounted on the Z-axis linear motion platform via a triangular connecting frame, and the rotation axis of the C-axis turntable is parallel to the Z-axis.

[0035] The U-axis micro-displacement platform is mounted on the C-axis rotary table;

[0036] The tool spindle and the Thyman Green interferometer are mounted on the U-axis micro-displacement platform via a mounting bracket.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] 1. This invention utilizes a Thyman-Green interferometer to detect the surface shape error of a hemispherical resonator. Through coordinated control of the machining tool, the surface shape of the sub-apertures is measured multiple times, and then the sub-aperture surfaces are spliced ​​together to obtain the complete surface shape of the hemispherical resonator. This enables real-time detection of the surface shape error of the hemispherical resonator during the ultra-precision polishing process, eliminating the need for off-machine inspection and reducing errors caused by repeated clamping. 2. This invention detects the surface shape of the hemispherical resonator in a non-contact manner, avoiding damage to the machined surface caused by contact measurement and effectively protecting the machined surface. 3. The in-situ surface shape detection results of this invention can further guide the writing of polishing CNC programs, achieving consistency in the quality of the hemispherical resonator and helping to improve the accuracy and efficiency of polishing. Attached Figure Description

[0039] Figure 1 This is the structure of an in-situ measurement system for the surface morphology of a hemispherical harmonic oscillator based on a Thyman-Green interferometer, as described in this embodiment of the invention. Figure 1 ;

[0040] Figure 2 This is the structure of an in-situ measurement system for the surface morphology of a hemispherical harmonic oscillator based on a Thyman-Green interferometer, as described in this embodiment of the invention. Figure 2 ;

[0041] Figure 3 This is a schematic diagram of the sub-aperture division in an embodiment of the present invention.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1-Machine bed, 11-X-axis linear motion platform, 12-Y-axis linear motion platform, 13-Z-axis linear motion platform, 14-C-axis rotary table, 15-U-axis micro-displacement platform, 16-Workpiece spindle, 17-Tool spindle, 2-Triangular connecting frame, 3-Fixed frame, 4-Worktable, 5-Tyman Green interferometer. Detailed Implementation

[0044] To enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments or examples are merely some, not all, of the embodiments or examples of the present invention. All other embodiments or examples obtained by those skilled in the art based on the embodiments or examples of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0045] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0046] Specific Implementation Scheme 1: This invention provides an in-situ measurement method for the surface topography of a hemispherical harmonic oscillator based on a Thyman-Green interferometer, such as... Figure 1 and Figure 2 As shown, the in-situ measurement method is based on an in-situ measurement system integrating a Thyman-Green interferometer and a hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool, and includes the following steps:

[0047] S100. For the polished hemispherical resonator, adjust the X-axis linear motion platform 11, Y-axis linear motion platform 12, Z-axis linear motion platform 13, C-axis turntable 14 and U-axis micro-displacement platform 15 so that the center of the hemispherical resonator coincides with the focal point of the lens of the Thyman Green interferometer 5.

[0048] S200, the C-axis turntable 14 drives the Thyman Green interferometer 5 to rotate, so that the field of view of the Thyman Green interferometer 5 includes part of the circumferential region of the hemispherical harmonic oscillator.

[0049] S300. Determine the initial measurement position of the hemispherical harmonic oscillator and measure the initial position sub-aperture surface shape using a Thyman Green interferometer 5.

[0050] S400, the workpiece spindle 16 drives the hemispherical resonator to rotate, and according to the specific angle calculated by the sub-aperture splicing algorithm, the current sub-aperture surface shape is measured by the Thyman Green interferometer 5, and there is an overlapping part between two adjacent sub-apertures;

[0051] S500. Repeat step S4 until the entire circumferential region of the hemispherical harmonic oscillator is measured.

[0052] S600: By splicing together all the sub-aperture surface data, the circumferential region morphology of the hemispherical harmonic oscillator is obtained.

[0053] Specific implementation scheme two: Step S100 includes the following steps:

[0054] S110. For the polished hemispherical resonator, the relative position of the C-axis turntable 14 and the hemispherical resonator is determined by the tool setting operation, and the X-axis linear motion platform 11 and the Y-axis linear motion platform 12 are adjusted so that the center of the hemispherical resonator coincides with the rotation axis of the C-axis turntable 14.

[0055] S120. Adjust the Z-axis linear motion platform 13 so that the focal point of the lens of the Thyman Green interferometer 5 is at the same horizontal level as the center of the hemispherical harmonic oscillator.

[0056] S130. Adjust the U-axis micro-displacement platform 15 so that the focal point of the lens of the Thyman Green interferometer 5 coincides with the center of the hemispherical harmonic oscillator. The rest of this implementation scheme is the same as in specific implementation scheme one.

[0057] Specific Implementation Scheme 3: The overlapping portion between two adjacent sub-apertures in S400 accounts for 20% of the sub-aperture area. All other aspects of this implementation scheme are the same as Specific Implementation Scheme 2.

[0058] Specific Implementation Plan Four: (e.g.) Figure 3 As shown, the sub-aperture stitching algorithm stitches together multiple adjacent sub-aperture surfaces with overlapping areas into a large-area complete surface. Due to misalignment errors during the measurement process, the topographic measurement results of two adjacent sub-apertures in the overlapping area at the same measurement position may be different. Therefore, it is necessary to correct the six-degree-of-freedom pose error in the sub-aperture measurement process by matching the optimal overlapping area, thereby reconstructing the circumferential surface of the entire hemispherical harmonic oscillator.

[0059] The measurement data for the sub-apertures of the Thyman-Green interferometer are (x, y, z), where (x, y) are the horizontal and vertical coordinates on the image plane, and z is the height value; the measurement data for the k-th sub-aperture is (x...y...z). k y k , z kThe measurement data for the t-th sub-aperture is (x t y t ,z t );

[0060]

[0061] Where g is the pose transformation matrix; (x q y q , z q () represents the coordinates of the sub-aperture data of the hemispherical harmonic oscillator in the global coordinate system.

[0062] In the global coordinate system, the measurement data deviation in the sub-aperture overlap region is:

[0063] d=<(x k y k , z k )-q,n>-<(x t ,y t ,z t )-q,n>

[0064] Where {q} is the point set projected from the medium aperture measurement data onto the surface of the hemispherical harmonic oscillator, and n is the unit normal vector of the hemispherical harmonic oscillator surface at position q; <(x k ,y k ,z k )-q,n> is a vector (x k ,y k , z k The inner product of q and vector n; <(x) t y t , z t )-q,n> is a vector (x k ,y k , z k The dot product of -q and vector n;

[0065] Based on the least squares method, the measurement data deviation in the overlapping region of the sub-apertures is minimized to obtain the surface morphology of the hemispherical harmonic oscillator;

[0066]

[0067] Where, N o This represents the total number of overlapping point pairs.

[0068] In this implementation scheme, the measurement range (f-number) and focal length (R-number) of the spherical lens of the Thyman Green interferometer are limited, preventing the complete surface shape of the spherical shell from being measured in one go. Therefore, the "piece together small parts" approach is adopted, measuring portions of the spherical shell (i.e., sub-apertures) multiple times and then piecing together the surface shapes of these portions to obtain the complete surface shape of the hemispherical resonator shell. Other aspects of this implementation scheme are the same as in specific implementation scheme three.

[0069] Specific implementation scheme five: The in-situ measurement system integrates a hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool and a Thyman Green interferometer 5. The hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool includes a machine bed 1, an X-axis linear motion platform 11, a Y-axis linear motion platform 12, a Z-axis linear motion platform 13, a C-axis rotary table 14, a U-axis micro-displacement platform 15, a workpiece spindle 16, a tool spindle 17, a triangular connecting frame 2, a fixed frame 3, and a worktable 4.

[0070] The machine tool bed 1 is equipped with an X-axis linear motion platform 11, a Y-axis linear motion platform 12 and a Z-axis linear motion platform 13. The X-axis linear motion platform 11 and the Y-axis linear motion platform 12 are stacked in a cross shape. The Z-axis linear motion platform 13 is installed perpendicular to the X-axis linear motion platform 11 and the Y-axis linear motion platform 12, together forming a spatial rectangular coordinate system.

[0071] The worktable 4 is mounted on the X-axis linear motion platform 11 and the Y-axis linear motion platform 12.

[0072] The workpiece spindle 16 is mounted on the worktable 4, and the rotation axis of the workpiece spindle 16 is parallel to the Y-axis.

[0073] The C-axis turntable 14 is mounted on the Z-axis linear motion platform 13 via a triangular connecting bracket 2, and the rotation axis of the C-axis turntable 14 is parallel to the Z-axis.

[0074] The U-axis micro-displacement platform 15 is mounted on the C-axis turntable 14.

[0075] The tool spindle 17 and the Thyman Green interferometer 5 are mounted on the U-axis micro-displacement platform 15 via a mounting bracket 3. Other aspects of this implementation scheme are the same as in specific implementation scheme four.

[0076] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for in-situ measurement of the surface topography of a hemispherical harmonic oscillator based on a Thyman-Green interferometer, characterized in that: The in-situ measurement method is based on an in-situ measurement system integrating a Thyman Green interferometer and a hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool, and includes the following steps: S100. For the polished hemispherical resonator, adjust the X-axis linear motion platform (11), Y-axis linear motion platform (12), Z-axis linear motion platform (13), C-axis turntable (14) and U-axis micro-displacement platform (15) so that the center of the hemispherical resonator coincides with the lens focus of the Thyman Green interferometer (5). S200, the C-axis turntable (14) drives the Thyman Green interferometer (5) to rotate, so that the field of view of the Thyman Green interferometer (5) includes part of the circumferential region of the hemispherical harmonic oscillator; S300. Determine the initial measurement position of the hemispherical harmonic oscillator and measure the initial position sub-aperture surface shape using a Thyman Green interferometer (5). S400, the workpiece spindle (16) drives the hemispherical harmonic oscillator to rotate, and the Thyman Green interferometer (5) is used to measure the surface shape of the current sub-aperture. There is an overlap between two adjacent sub-apertures. S500, Repeat step S400 until the entire circumferential region of the hemispherical harmonic oscillator is measured; S600: By splicing together all the sub-aperture surface data, the circumferential region topography of the hemispherical harmonic oscillator is obtained; Step S100 includes the following steps: S110. For the polished hemispherical resonator, the relative position of the C-axis turntable (14) and the hemispherical resonator is determined by the tool setting operation. The X-axis linear motion platform (11) and the Y-axis linear motion platform (12) are adjusted so that the center of the hemispherical resonator coincides with the rotation axis of the C-axis turntable (14). S120. Adjust the Z-axis linear motion platform (13) so that the focal point of the lens of the Thyman Green interferometer (5) is at the same horizontal level as the center of the hemispherical harmonic oscillator. S130. Adjust the U-axis micro-displacement platform (15) so that the focal point of the lens of the Thyman Green interferometer (5) coincides with the center of the hemispherical harmonic oscillator; In S400, the overlap between two adjacent sub-apertures accounts for 20% of the sub-aperture area; The algorithm for stitching together the sub-aperture surface shape data includes the following steps: The measurement data for the sub-aperture of the interferometer are (x, y, z), where (x, y) are the horizontal and vertical coordinates on the image plane, and z is the height value; the measurement data for the k-th sub-aperture are (x...y...z...). k ,y k ,z k The measurement data for the t-th sub-aperture is (x t ,y t ,z t ); Where g is the pose transformation matrix, (x q ,y q ,z q () represents the coordinates of the sub-aperture data of the hemispherical harmonic oscillator in the global coordinate system; In the global coordinate system, the measurement data deviation in the sub-aperture overlap region is: Where {q} is the point set of the sub-aperture measurement data projected onto the surface of the hemispherical harmonic oscillator, and n is the unit normal vector of the surface of the hemispherical harmonic oscillator at position q; For vector (x) k ,y k ,z k The dot product of -q and vector n; For vector (x) t ,y t ,z t The dot product of -q and vector n; Based on the least squares method, the measurement data deviation in the overlapping region of the sub-apertures is minimized to obtain the surface morphology of the hemispherical harmonic oscillator; Where, N o This represents the total number of overlapping point pairs.

2. The in-situ measurement method for the surface topography of a hemispherical harmonic oscillator based on a Thyman-Green interferometer according to claim 1, characterized in that: The in-situ measurement system integrates a hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool and a Thyman Green interferometer (5). The hemispherical harmonic oscillator ultra-precision grinding and polishing machine tool includes a machine bed (1), an X-axis linear motion platform (11), a Y-axis linear motion platform (12), a Z-axis linear motion platform (13), a C-axis rotary table (14), a U-axis micro-displacement platform (15), a workpiece spindle (16), a tool spindle (17), a triangular connecting frame (2), a fixed frame (3), and a worktable (4). The machine tool bed (1) is equipped with an X-axis linear motion platform (11), a Y-axis linear motion platform (12) and a Z-axis linear motion platform (13). The X-axis linear motion platform (11) and the Y-axis linear motion platform (12) are stacked in a cross shape. The Z-axis linear motion platform (13) is installed perpendicular to the X-axis linear motion platform (11) and the Y-axis linear motion platform (12), together forming a spatial rectangular coordinate system. The worktable (4) is mounted on the X-axis linear motion platform (11) and the Y-axis linear motion platform (12); The workpiece spindle (16) is mounted on the worktable (4), and the rotation axis of the workpiece spindle (16) is parallel to the Y-axis. The C-axis turntable (14) is mounted on the Z-axis linear motion platform (13) via a triangular connecting bracket (2), and the rotation axis of the C-axis turntable (14) is parallel to the Z-axis. The U-axis micro-displacement platform (15) is mounted on the C-axis turntable (14); The tool spindle (17) and the Thyman Green interferometer (5) are mounted on the U-axis micro-displacement platform (15) via a mounting bracket (3).

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